Oxygen transport during dopamine infusion in dogs

Catecholamines increase not only oxygen delivery to tissues but also oxygen consumption (VO2). The effect of an infusion of dopamine hydrochloride has been studied at two doses, each in six dogs. Dopamine 10 micrograms kg-1 min-1 caused an increase in haemoglobin concentration and altered cardiac output, oxygen availability and total body oxygen consumption such that oxygen availability ratio increased and (CaO2-CVO2) decreased although these changes were not statistically significant. Dopamine 30 micrograms kg-1 min-1 increased (P less than 0.05) heart rate, haemoglobin concentration and CaO2 and significantly reduced stroke volume and VD/VT. Although oxygen availability increased, increases in oxygen consumption were greater and this resulted in a statistically insignificant reduction in oxygen availability ratio and an increase in (CaO2-CVO2). Terminating the dopamine infusion resulted in significant (P less than 0.05) decreases in cardiac output, PVO2, CaO2), oxygen availability and oxygen consumption and an increase in (CaO2-CVO2). It was concluded that maximum oxygen delivery occurs at a lower dose than that required to produce the maximum increase in oxygen consumption.